Textural variations in Neogene pelagic carbonate ooze at DSDP Site 593, southern Tasman Sea, and their paleoceanographic implications

Author(s): Cooke, Penelope J.; Nelson, Campbell S.; Crundwell, Martin P.; Field, Brad D.; Elkington, E. Shirley; Stone, Harold H.
Author Affiliation(s): Primary:
University of Waikato, Department of Earth Sciences, Hamilton, New Zealand
Institute of Geological and Nuclear Sciences, New Zealand
Volume Title: Ballance special issue II; aspects of tectonic, volcanic and sedimentary geology of the New Zealand region
Volume Author(s): Nelson, Campbell S., editor
Source: Ballance special issue II; aspects of tectonic, volcanic and sedimentary geology of the New Zealand region, edited by Campbell S. Nelson. New Zealand Journal of Geology and Geophysics, 47(4), p.787-807. Publisher: Royal Society of New Zealand, Wellington, New Zealand. ISSN: 0028-8306 CODEN: NEZOAY
Note: In English. Institute of Geological and Nuclear Sciences Contribution No. 3237; accessed on April 26, 2006. 113 refs.; illus., incl. 4 tables
Summary: Changes in Neogene sediment texture in pelagic carbonate-rich oozes on the Challenger Plateau, southern Tasman Sea, are used to infer changes in depositional paleocurrent velocities. The most obvious record of textural change is in the mud:sand ratio. Increases in the sand content are inferred to indicate a general up-core trend towards increasing winnowing of sediments resulting from increasing flow velocity of Southern Component Intermediate Water (SCIW), the forerunner of Antarctic Intermediate Water. In particular, the intervals c. 19-14.5 Ma, c. 9.5-8 Ma, and after 5 Ma are suggested to be times of increased SCIW velocity and strong sediment winnowing. Within the mud fraction, the fine silt to coarse clay sizes from 15.6 to 2 µm make the greatest contribution to the sediments and are composed of nannofossil plates. During extreme winnowing events it is the fine silt to very coarse clay material (13-3 µm) within this range that is preferentially removed, suggesting the 10 µm cohesive silt boundary reported for siliciclastic sediments does not apply to calcitic skeletal grains. The winnowed sediment comprises coccolithophore placoliths and spheres, represented by a mode at 4-7 µm. Further support for seafloor winnowing is gained from the presence in Hole 593 of a condensed sedimentary section from c. 18 to 14 Ma where the sand content increases to c. 20% of the bulk sample. Associated with the condensed section is a 6 m thick orange unit representing sediments subjected to particularly oxygen-rich, late early to early middle Miocene SCIW. Together these are inferred to indicate increased SCIW velocity resulting in winnowed sediment associated with faster arrival of oxygen-rich surface water subducted to form SCIW. Glacial development of Antarctica has been recorded from many deep-sea sites, with extreme glacials providing the mechanism to increase watermass flow. Miocene glacial zones Mi1b-Mi6 are identified in an associated oxygen isotope record from Hole 593, and correspond with times of particularly invigorated paleocirculation, bottom winnowing, and sediment textural changes.
Year of Publication: 2004
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 07 Marine Geology and Oceanography; Carbonate sediments; Cenozoic; Challenger Plateau; Clastic sediments; DSDP Site 593; Deep Sea Drilling Project; IPOD; Leg 90; Neogene; Ooze; Pacific Ocean; Paleo-oceanography; Pelagic environment; Sediments; South Pacific; Southwest Pacific; Tasman Sea; Tertiary; Textures; West Pacific
Coordinates: S403029 S403028 E1674029 E1674028
Record ID: 2006038648
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by Institute of Geological and Nuclear Sciences Limited (GNS Science), Lower Hutt, New Zealand